What add's to idle air in gear?

[MikeOD]

I'm not really sure what's adding to my idle air in gear. I tried setting all transmission shift airflow numbers to zero's and to very low numbers, and I don't see any difference.

In this log, I waited for the truck to settle into the 850 rpm desired idle. It's not the most stable idle, but it's a pretty big cam. I'm trying to work through the base idle airflow table in order to smooth it out as best I can.

The log starts with the truck in park. At 5 seconds, I click it into reverse. You'll see the throttle correct a little, but overall the RPM stays in a similar range, it's got a Circle D 3400 stall converter, so there's not much difference in load from the transmission at 850 RPM in gear or in neutral.

At 15 seconds, I click it into neutral, and then at 20 seconds, I click it into overdrive.

The moment I put the shifter into OD, the TPS increases from 18.8 to 24.7, and you'll see that my RPM is now 1000+, even though commanded is still 850. Idle adaptive advance is trying to pull the RPM down, but it can't, and the throttle will literally stay like this no matter how long I drive...every time I come to a stop, the engine is pushing against the converter. I tried pulling air out of the in gear rows of the airflow final minimum table, but it doesn't seem to matter. Something is adding airflow, and I don't know what.

Any advice where else to look? Any differen't PID's that I should scan?

idle air.hpl
Rev7.hpt

[MikeOD]

Well I feel pretty stupid...in the Integral Idle Airflow table...I had all positive numbers...so when RPM is above or below, it would add, and just end up at a max amount added...and so did the stock 2009 LY6 van file. So I guess the stock LY6 idle is stable enough that it never uses the integral airflow correction, or every one of them would do this in gear? Looking at a 2010 Camaro SS I see this too. I'm a little confused about this table, if anyone could clarify how ECM 12195 works, that would help me a bunch.

[MikeOD]

Can't put negatives in the integral table, and the comment says that when error is positive, it knows to subtract this from idle, and when error is negative to add...so I'm still lost for what's adding airflow to my idle when I click the shifter into gear.

[Area47]

whats the cam specs? Have you reverted back to the stock idle settings across the board?

[MikeOD]

The engine is a 454, the cam is 243/255 .664/.670 114 +4.

It won't even try to run on stock idle settings. If I go to all stock except for commanded RPM and airflow final minimum I have this same problem. It'll get close to target RPM in neutral, but it'll just instantly add throttle and fight the brakes when I put it in drive.

Also, it's fine in reverse. What idle settings are different from R to D? I have the same numbers in the airflow final minimum table for both so I don't know what causes the difference.

[gmtech16450yz]

I'm guessing it wouldn't run on the stock idle settings because the idle timing is down below 10- often as low as 3 degrees! Get that idle timing up to at least 15-20 degrees. Like area47 said, try getting back closer to stock settings. You've got a lot of tables REALLY far away from stock. Why is the area scaler lower than stock?

Here's another thing I noticed that I think many guys don't realize... There are some tables like "Startup Idle Speed" that show "Engine Coolant Temp" as the temp axis. Notice it doesn't have the little (*F) after it? Those values are in Celsius. It's not going to fix your issue, but you have that table set up like it's in Fahrenheit and it's not. Don't feel bad, I think there's A LOT of guys out there that get stung on that. You have to use the conversion tool to see what the temps are in Fahrenheit when setting up that table.

When all else fails, always try to revert back as close to stock as possible. I'd like to see how the idle numbers come out with more ignition timing, which would also make it run way better.

[Area47]

even on large cams, it's extremely rare that i mess with the adaptive/proportional tables to cure an issue. base air flow and timing tables are the major players in it. setting the base timing in gear, or idle at 17-20 degree's would smooth it out a bit and gain a bit more control. working the base air flow around this to get the commanded rpm and timing in line really shouldn't take a lot of work. for that size of motor, the cam isn't huge by any means.

[MikeOD]

I see what you guys are saying. I was screwing with the scalar when I posted this last tune. I have had it idle with 17 even 20 degrees before, but it doesn't matter...it idles great in park, neutral and reverse, but in any forward gear, something I don't have access to is adding a ton of air to it and making it fight the brakes.

I know the cam isn't by any means huge, but I really think there's a table I'm missing access to that's telling it to add air in forward gears.

I have a mechanical issue to fix when the engine bay cools down, then I'll get back after this hopefully tomorrow. I have a couple days off from the day job and wanted to get this truck tuned for my uncle. It's pretty cool, 1990 454SS with a custom build LSX454 and a Jake's 4L80E with a Circle D converter...it's got great smooth power at full throttle but that's the easiest part of the tune for me, I really want to get the idle and drive ability nicer for him so he can just turn the key and enjoy it.

[GHuggins]

Stupid question, but have you tried lowering the brake and max brake percent settings?

[gmtech16450yz]

I seriously doubt that it's a table you don't have access to. These engines have been around for a couple decades, HPT has pretty much covered all the bases on tables for this old stuff.

Get those tables back closer to stock, lock in a decent ignition advance number at idle by making the main and idle spark tables the same and then try shutting off ALL adaptive idle control so you can get your min air rates close. When the tables are so far off, you end up with weird issues because none of the tables are getting along with each other properly.

It's air+ignition timing+fuel mixture. You HAVE to have those close WITHOUT any error modifications or control. You know what idle mixtures should be, airflow should be a ballpark of ~~~~~~8 to 12% throttle and ignition timing needs to be at least 15-20 degrees. You can't expect any of the idle controls to work properly when the engine is trying to run on 3 degrees of ignition timing.

There are a bunch of threads right now on idle and decel stuff. Maybe the first step for you guys is exactly what I suggested just now, shut off ALL adaptive idle controls and get the basics right before changing anything else. Then you should be able to turn the adaptive tables back on with bone stock settings and be fine 90% of the time.

[MikeOD]

So I turned all the adaptive stuff off... That I have access to. I start the engine, I use the throttle to help it find idle, which my final airflow minimum ends up right at 840 rpm with 13 degrees of timing and very stable injector pulse, commanded lambda is 1.00 and my wideband shows less than 1% error.

The instant I move the shifter from neutral to reverse, the TPS doesn't move, injector pulse doesn't change, timing doesn't change, rpm ends up at 830 because of the transmission.

Move the shifter back to neutral, RPM back to 840.

Move the shifter to any forward gear, TPS comes up roughly 4%, rpm climbs immediately to 1250.

So again I ask, other than proportional and integral airflow, and the final airflow minimum table, and the shift airflow tables, all of which I've set to zero, what else can add to the idle airflow in a forward gear?

[MikeOD]

Stupid question, but have you tried lowering the brake and max brake percent settings?

I did, but then cold start sucks because it can't give it the air it needs for the higher commanded RPM as it warms up.

[GHuggins]

Contrary to what some on here may say - there are controllers within the background of the OS's themselves that will wreak havoc on how a vehicle idles and controls idle with loads... Have you by chance tried a different OS other than a 6l gvan? Wondering if a 7l car or a 6.2l truck would make any difference?

[gmtech16450yz]

Ok I re-read your situation. You've mentioned since the beginning that this issue ONLY happens when the trans is put in a forward gear. Why aren't you looking at an actual trans issue? What trans/TCM is in this truck? Is it compatible with the ECM/OS?

Ok, I just looked at your tune and saw this in trans diag...




Ummmmmm, what's going on here? Is it setting a PRNDL code? Is your hardware (Engine/ECM/Trans/TCM) incompatible causing an error and in turn defaulting to a higher idle speed?

I think I would be trying one or both of these things at this point...

Stand back and look at the WHOLE picture as far as the entire engine/trans goes.

Think about changing the PRNDL settings in the tune to simply eliminate it thinking it's in any of the forward gears and instead use the bit for reverse as also the input for forward gears. This is a highly modified tune in a modified hardware configuration. Sometimes you just have to back up and fix a problem by eliminating the situation the problem occurs in. You have an issue that makes the truck pretty much undriveable. How many issues will you have that could make it undriveable by simply not letting it get the input that makes the idle too high? Maybe none?

Obviously finding and fixing the issue is the first choice. From what I'm seeing, I'd be looking at the TCM and PRNDL itself.

[MikeOD]

It's got a 4L80E. The PCM and TCM are both from an 09 van which was a factory 4L80E truck.

I'm working with a base that's from Speartech because they built the wiring harness. I'll take a more in depth look at an original van tune against this as well as seeing if I have the same prndl setup.

[MikeOD]

I changed the bits in the PRNDL table in the TCM, then I changed them back...and now the issue is gone. I literally copy and pasted back from the previous file that was having issues.

[BAH25]

I changed the bits in the PRNDL table in the TCM, then I changed them back...and now the issue is gone. I literally copy and pasted back from the previous file that was having issues.

Sorry to bring back a dead post. I am having this EXACT same issue on a swapped vehicle. I can not for the life of me figure out why this is happening. I tried changing the bits in the PRNDL table and then back to the original but it did not help, even a write entire. Is this the only thing you changed? Thanks